Performing Global Navigation Satellite System (GNSS) receiver acquisition without knowledge of current time, receiver's position, and satellite's almanac can require a significant amount of time. The reason for this is that all satellites from a given constellation must be searched as it is not possible to know in advance which satellites are visible. The advent of future multi-constellation receivers (capable of processing signals form several constellations like GPS, GLONASS, Galileo, and Beidou) will make this task even more demanding. In addition, most new signals (like GPS L5 and Galileo E1) have longer primary codes which translate directly into longer search time per satellite.
In many applications, a key performance indicator of the GNSS receiver is the time required to acquire enough satellites to obtain a position fix, usually called Time to First Fix (TTFF). Thus, it is desirable to reduce the time to first fix as much as possible.